Gyrocompass



J. B. HENDERSON April 19, 1927.

GYROCOMPAS S Filed Aug. 29. 1919 2 Shasta-Shoot 1 Vlllllll VENTOR 1625 61 April 19, 1927. L B. HENDERSON y ,3

GYRocoMPAss Filed Aug. 29, 1919 2 Sheets-Shoot 2 Eig. Z.

ATTORNEY ibm, Nxmll BY @y y This invention Patented Apr. 1.9, 1927.

UNITED STATES.I

JAMES BLACKLOCK HENDERSON, 0F LEE, ENGLAND.

GYRCOMPASS.

Application' led August 29, 1919, Serial No.

relates to improvements in gyro Compasses and has .for its object the elimination of the errors due to any periodic motion of the ship, airship or airplane upon which the compass is mounted.

In gyro Compasses as -heretofore constructed, one f the chief objections to their use has been the deviation introduced in rolling or pitching motion of the ship, airship orairplane upon which the com ass is mounted. In order to overcome this eviation, modifications have been suggested and used, involving the use of several gyroscopes upon the compass with the object of reducing the couple about the vertical axis which produces the deviation.` The arrangement of multiple gyroscopes reduces the arm of this couple. More specifically` it is the object of my invention to reduce this disturbing couple by annulling the forces of the couple when usin a single gyroscope. The compasses hereto ore constructed have been employing pendular devices for providing the gravity control upon the gyroscopes as was first used by Foucault. In the arrangement according-to my invention the gravity control is provided by a Huid system, the di'erence between it and the pendulum being that the gravity control is normally in neutral equilibrium and the gravity forces accumulate slowly as the axis of the gyroscope tilts from the horizontal plane, or in other words, the gyroscope and the fluid system are both in neutral equilibrium until it tilts from its normal position.

It is also the object of my invention to provide` a follow-up system which is con- `tinually oscillatin lr about the vertical axis without the introduction of any sources of power other than that required to drive the gyroscope rotor with the object of reducin the friction upon the vertical trunnions o the gyroscope. It is further an object to provide this follow-up system without any f Vmechanical connection between it and the gyroscope. v

It is also an object of my invention to introduce an oscillating frame for supporting the horizontal tru'nnions ofthe gyroscope with the object of reducing the friction of the same, the said oscillation being obtained by the power supplied to the` gyroscope rotor.

It is the further object of my invention to provide the forces required to'damp, the oscillation of the compass by means 0f power objects in view,

320,6s1, ami-m arm mann may 1s, 191s.

taken from the gyroscope rotor by improved devices.

Otherobjects of the invention will be apparent from the detail description hereinafter to follow and with these and other the `invention consists of the constructions herein described and specifically pointed out in the appended claims.

In the drawing, Figure 1 is an elevation of the gyro compass viewed from the north side, parts being shown in section for clearness.

Figure 2 is a side elevation partially in section on the line AB of Figure 1.

Fi 3 is a detail of the cup containing the liquid forming part of the level; Fig. 4 isa detail of the ball bearing support for the bracket which carries the level, and Fig. 5 is a detail of the chute or deflector.

The gyroscope comprising a gyro wheel 1 within its case 2 is only partially shown and is of the usual constructlon driven by three phaseelectric currents as Will be later referred to.' The case 2 is supported upon two pivots 3 and 4; the pivot 3 rests in a conical recess or depression 5 in a boss 6 carried by a ring 7; the pivot 4 rests in a V groove 8 in a boss 9 also carried by the ring 7. The two bosses 6 and 9 and the conecting ring 7 are supported on two ball bearings 10 and 11 in a imbal ring 12. This gimbal ring 12 and t e parts hereinafter described associated therewith is thus able to make a complete turn around the horizontal trunnions of the gyroscope whereas for small os cillations of the gimbnl ring, the ball bearings 10 and 11 are not brought into play the oscillation being taken by the motion of the pivots 3 and 4 relatively to the ring 7. It isalso evident that since the pivot 3 is mounted in a cone shape seat and the pivot 4 in a V groove 8, the gyroscope casing is ermitted to ex and or contract without afecting the sensitiveness of its mounting.

The inner gimbal ring 12 is carried by the follow-up ring 13 which forms a part of thefollow-up system as will later be referred to, upon two ball bearings 14 and 15 about the vertical axis, the weight being carried by the suspension wire 16 in a manner well known in the art. The follow-up ring 13 is supported by a ring 17.011 ball bearings 18 and 19 about the vertical axis. The bearing 19 has a thrust ball 2O upon which the post 21 carried by the ring 13 rests, which bearing supports the weight of the gyroscope,- its gimbal rings and follow-up ring. The ring 17 is carried by ordinary gimbal rings, one of which 22 is carried upon horizontal trunnions 23 as is the usual construction. t

The gyro casing 2 has three ports 24 for the admission of air and three Ijets of air emerge from the case through orifices 25, 26 and 27. The jet emerging through the orilice 25 serves to actuate the follow-up mechanism= the jet emerging through the orifice 26 servesl to damp the oscillation ot' the compass and the jet through the orifice 27 serves to oscillate the ring 7, thus reducing the friction upon thepivots 3 and 4.

Referring first to the follow-up mechanism, the jet from the orifice 25 passes through a passage 28 in the boss 9 and upon emerging from the passage 28 it enters a cylindrical chute 29 carried by the follow-up ring 13. This chute consists ot' a hollow cylindrical box having a closed bottom 29, see Fig. 5. and divided vertically by a diaphragm 30. The box has two apertures 31 and 31"l at its closed end which are diametrically opposite in a horizontal plane. The diaphragm 30 is helical in form and twists through I180 degrees in the length of the box 29 so that the air entering on the near side of' the diaphragm leaves the box through the hole 31 which is on the far side ofthe diaphragm and vice versa. Thus the jet emerging from the passage 28 tends to keep the box 29 co-axial with the jet and when the ring 12 precesses as will be further described, this jet of air causes the follow-up element to remain in alignment with the ring 12 since any relative movement between the two rings will cause the air jets emerging from openings 31 to be unequal and causea torque which will act on ring 13 to cause 1t to follow ring 12.

The jet from the orifice 27 enters a. chute 32 carried by the ring 7, similar in .all respects to the chute 29. The ring is thus ke )t in register with the jet emerglng from orifice 27 and is continually oscillatingr duc to the eddies in the air jet. It, therefore, tends to eliminate the friction upon the pivots 3 and 4. j

The jet 26 which operates the damping mechanism is associated with the gravity control system which will now be described. This system consists of two vertical cylindrical tubes, or vessels. and 5l provided with glass windows 52. The tops of these tubes are closed by screw covers 53 each of which contain a ball valve 54 (see Fig. 3) which permits the ingress of airand prevents the leakage of the fluid within the tubes as will .be later referred to.

The two tubes 50 `and 51 are inter-onnected by a. curved tube 55 and a rod 56` which encircle the gyro casing. The bore of the tube '55 is small in diameter as shown by the dotted line in Fig. 1 of the drawing to provide a capillary tube. The combination of the tubes, or vessels, 50, 51 and 55 forms a level which is partially filled with viscous fluid such as mercury and the capillary tube 55 insures that the passage of fluid from one tube to another will take p'lace at a very slow rate. This fluid system is supported by two brackets 57 and 58 connected respectively to the tube 55 and the rod 56. These brackets are supported on small trunnion pivots 59 and 60 carried by ball bearings 61 and 62 at'- lixed to the gyro casing. One of these ball bearings is shown in detail in Fig. 4. The level is adjusted so that it is normally in neutral equilibrium on the trunnions 59 and 60, the adjustment being made by the adjustable weights 63 and 64. The motion of the level about this trunnion axis is constrained by two springs 65 and 66 which are connected at one end to the rod 56 and at their other ends to adjustable hooks 67 and 68 carried by the gyroscope casing 2, whereby the tension of these springs may be adjusted. The bracket- 57 carries a chute 70 which is of a altern similar to the chute 29 already described. This chute is pivoted about an axis 71 and can be angularly adjusted by means of a screw 72 so that the diametral partition across the chute is centrally disposed with respect to the' jet. The jet emerging from the orifice 26 enters the chute 70 and tends to cause the level to follow the gyro case when it tilts in addition to the constraint supplied for this purpse by the springs 65 and 66. YThe jet on emerging from the lower end 73 in the chute 70 also supplies the forces required to damp the oscillation of the compass as will be described in the operation-of the compass.

The torsional4 stiffness of the suspending wire 16 is reduced or annulled by means of a cross spring 75 which connects the bracket 76 attached to the follow-up ring 13 and the bracket 77 attached to theinner gimbal ring 12. It will be evident that any tension in this spring 75 applies torsional instability between the two rings V12 and 13 and by making the torsional instability due to the spring 75 equal to the torsional stability produced by the suspension 16, the connection between elements 12 and 13 may be torsionally neutral and thus reduce the forces on the gyroscopc due to any lag of the followup system.

As is the usual construction the follow-up element 13 carries a compass card 80 which is read opposite the `lubbers line l carried by the outside ring 17.

The suspension 16 is attached at its upper end to a bolt 82 which may be raised or lowered by the nuts 83 and may be turned by a screw adjustment 84. the screw 84* being supported by a lug 84" on a bracket 84' carried by the sleeve 84". The screw acts 5 16, thence to through an arm 84 attached to the bolt 82.

, A mirror 85 is. attached to the. gyro casing 2 for the purpose of detecting small deections by making adjustment of the comass.

The three .phase electrical connections are conveyed to the gyroscope as follows: one to the trunnion bearing 23 by wire 23", second to the trunnion ring 22 of the gimbal ring by wire 22, and the 3rd to ground by wire 22".

Phase one is connected to the lubbers line 81 b wire 81 and the brush 86 to the insulate bolt 82 and the metallic suspension the insulated bushing 87 from the ring 12, then by a wire connection 87 to the outer race of the ball bearing 10 through the balls to the inner race, thence by a Wire to the flexible connection 88 between the rings 7 and the gyro compass 2, then by the usualA wire connection to the gyro stator.

.Phase two passes by a wire 23* which is connected with the trunnionk 23 which is connected by a wire 23, passin along the ring 17 to the insulated Yball arings 19 `and 2() to the pivot 21 which is insulated and contains a small mercury cup 91 through which the current passes to the insulated vertical pivot 15, thence it is conveyed by a wire along the ring 12 toy a ball bearing 11 and through this ball bearing) in a similar Vmanner to that already descri ed 'for phase one, the current passing through the liexible connection to the o stator.

The 3rd phase whic isgrounded, passes through the ball bearings of the outer gimball rings to the ring 17, thence through the mercury in the ball bearing 18 to the ring 13, thence through bracket 76, the spring 75 and bracket 77 t0 the ring 12 (see Fig. 2), thence through the spring connection 95 to an insulated connection passing through the boss, thence throu h iexible connection 89 to the gyro case. he ound circuit may also pass from the bore 6 through the pivots 3 to the gyro casing but a wire connection is preferable to avoid an excess of current pasiing through pivot 3.

The level in addition to havin the,rbal anced weights 63 and 64 for raisin and lowering t e center of gravity, is litte also with the balancing weights 98 and 99 in Figure 2 for moving 'the center of gravi horizontally. The Qro case ish alsoprovid with balanced weig ts .100 for raising and lowering the center of gravity and 101 for the horizontal adjustment of the center of gravity. p

To use the compass, the level is rst balanced so that when the liquids stand at equal heights in the two tubes 50 and 51, is in neutral equilibrium on its trunnons 61` and 62. This adjustment is media by means of the adjustable weights 63 and .64, 98 and the level v nections havin axis maintaining its direction Yrame direction as the tilt of the gyro,

99. The springs 65 and 66 are thenitted to control the motion of the level relatively t to the gyro case and are adjusted so that when the gyro axis is horizontal the liquid stands at equal heights in the tubes 50 and 51. The gyro case is then balanced by means of the weights and 101 so that it is in neutral equilibrium on its pivots 3 and 4 and the gyroscope together with the rin 7 and the ring 12 relatively adjusted so that when the compass becomes inclined, the balance about the inclined vertical trunnions is perfect. This adjustment may be made by the screw adjustments provided in the ring 12 for the axial motion of the two' bosses 6 and 9. The follow-up 13 is also balanced on its vertical trunnions. The electrical conbeen connected, the power can be switche on to the gyroscope and the compass is ready for action. The connections are to made that the direction of rotation of the gyro rotor is in the opposite sense to the rotation of the earth.

Operation of the gyra-compass.

y Fig. 1 represents a view of the north side of the compass, the rotor revolving clockwise, i. e., in a direction opposite to the ea'rths rotation. Assume that the ro is set up with the rotor revolving and wlth its axis horizontal and deiiected trom the meridian, say to the east side. rrAssume, first of all, that the dam ing nozzle 26 is blocked. The gyro and the ui gravity control system 1t carries are together in neutral equilibrium on the pivots 3 and 4 So that the rotor axis tends to maintainja constant direction in space. The horizontal plane, however, does not maintain a constant direction in space but rotates about the N.-S. horizontal line with a velocity o cos A in which w is one revolution every 24 hours and the latitude so that if the latitude is 60 the horizontal plane makes one revolution about the N.-'S. line every 48 hours. The gyro in space radually acquires a tiltrelatively to the zontal plane not `due to a precessionalmotion but due to the horizontal plane moving awayfrom it. Thus if the north end be to the east of the meridian it gradually acquires an upward tilt. The fluidA in the tubes 55 then Hows from vessel 51 to vessel 50 and the level then acquires a further tilt in lhe t is further tilt beingconstrained by the springs 65 and 66 and being proportional to the tilt of the The center of gravity of the system as, therefore, been moved parallel to the rotor axis and corresponds to moving a weight alonlgl that axis by an amount proportional to t e tilt of the gyro.

This extra weight on the south end of the teva )lis ori-

o causes the rotor axis to precess the meridian but so long as the rotor is rising and the tilt gradually if the axis is to the east of the on the S. end and the velocity of procession it produces continue to increase, and the rotor axis passes the meridian with considerable tilt and horizontal velocity. The horizontal plane on the west side, however, diminishes, reducing the weight on the south end and the horizontal precessional velocity until the rotor axis again becomes horizontal when its deviation to the west is equal to its initial deviation to the east.

The rotor axis then acquires a downward tilt due to the horizontal plane on the west meridian, the weight i side continuing its upward motion and the rotor axis traces out below the horizontal planean elliptical path which is similar to the path which it previously traced out above the horizontal plane. The north end of the rotor axis thus traces out an ellipse relatively to the meridian the short vertical axis ofthe ellipse being in the meridian. The longer horizontal axis of the ellipse would not be exactly in the horizontal plane gvi'o were exactly in neutral equilibrium when set up With its rotor axis horizontal, it would be slightly above the horizontal plane by an amount suiicient' to produce a weight on the south end suiiicient toy cause a precession round the vertical equal to w sin A, which is the angular velocity of the meridian round the vertical due to the rotation of the earth. This steady smallzero tilt may be compensated by the addilion of a small Weight on the south end of,

the gyro. This is a common correction for latitude at present used and does not orm an essential feature of the invention apart from its use of the other combinations shown. t

The air jet emerging from nozzle 26 has the function of damping out this elliptic motion of the gyro axis so that it takes up the steady position represented by the center of the ellipse. The air jet divides upon the E.W. diametral partition across' the chute and the southern portion of the jet emerging through the hole in the chute being progected to the north, the northerly portion emerging through the opposite hole and being projected to the sout If these two portions are equal. no torque will act upon the gyro about the vertical axis but if the chute 70 is deflected relatively to the gyro by a flow of fluid or other cause the two jets leaving the chute will be unet ual and a torque about the vertical will resu t. The flow of fluid in normal working is proportional to the tilt of the yro axis, hence the air jet fro Q6 will pro uce a torque about the ver-tica t roportional to the tilt of the gyro axis. rFhis torque is in the direction to introduce a precession which reduces the tilt. The end of the rotor axis then instead yof this tilt being of describing continuously its elliptic orbit describes a spiral path towards the center of the orbit, and remains there.

The gravity control couples and thethe excess weight on the south end of the Y axis and there is no cumulative coin onent torque either about the vertical or horizontal axis due to rolling or pitchi-n when following a quadrantal course suc as exists in all compasses in which the gyroscope has pendular or inverted endular control.

The damping of t e oscillation of yrlli Compasses having pendular control produces torque about the vertical to damp the oscillation has in the past been limited by deviations of the com ass reduced by the dam ing mechanism w en t e ship is accelerated) along the meridian. These deviations are not produced simultaneously with the acceleration. The acceleration produces a torque about the vertical through the dampi mechanism which tilts the gyro axis an a deviation of the compass results quarter a period later. In my compass no ballistic or suddenly applied torque can be `brought into action by acceleration of the ship and the damping can, therefore, be increased greatly. It can be increased until the motion is simpl j dead-beat. It can, however, be increase still further as follows:

It will be evident from the arrangement of the air-chute 70 that the air-jet emerging from the nozzle 26 serves to constrain the fluid containers relatively to the ro case, thus assisting the action of the springs 65 and 66. If the' jet 26 be increased the spring forces may be diminished thus increasing the damping couples and diminishing the gravity control couples and if the jet be increased until it controls the level with- `out springs only the couples about the vertical remain. he gyro then only oscillates vertically and its position of rest is with its axis tilted by an amount roportional to the deviation from the meri ian. The amount roportional to the tilt by the level relative y to the gyro case can be read olf on a convenient scale and the deviation of the compass from the meridian is thereby known. The ro moves veryl slow- 1y towards the meridian due to the earths rotation the velocity with which it a preaches the meridian being w cosine of t e tilt of the rotor axis. This phase of the nsaid ring, a follow-up element surrounding" cess,

. of the instrumentl vention is more clearly described in my application Serial No. 382,676, ,iiled May 19, 1920.

I claim:

1. In a gyro compass, a gyroscope, a follow-up element associated withsaid gyroscope and fluid pressure means acting directly upon the follow up element for causu ing said follow-up element .to follow said gyroscope.

2,. In a gyro compass, a gyroscope, a follow-up element within which the gyroscope is mounted, Huid pressure means directly connecting the gyroscope and the follow-up element tor causing the element to lfollow the gyroscope and fluid pressure means for damping the oscillations of the gyroscope.

3. In a gyro compass, a roscope, a casing for said gyroscope, a fo low-up element and means associated with said gyroscope casing and said follow-up element for causing a jet of air discharged from said casing to act directly upon the follow-up element to cause it to follow said gyroscope and its casing.

4. In a yro compass, a gyroscope, a casing for said gyroscope having an air inlet and an air outlet, a supporting ring surrounding said gyro casing and provided with a passage registering with the outlet, pivotal connections between said casing an said ring and a chute carried by said followup element arranged in alignment with said passa e whereby the air directed towards said c ute will cause said follow-up element to remain in alignment with said gyro casing and said ring. 5. In a gyroscopic instrument, a gyroscope, a member within which the gyroscope is mounted, a second member on which t e first named member is mounted, one of said members being provided at one side of the instrument with a substantially conicalfrea pin associated with the other member and coactng with the recess, one of said members being provided at the other side and a pin associated with the other member `and coacting with the last named recess. 6. In a gyro compass, a gyroscope and its casing, a rin surrounding said gyro casing and supporting said gyroscope and its casing upon a horizontal airis, a second ring surrounding said first named ring and supporting said first named ring about a honzontal axis, said second named ring being supported upon a vertical axis and an unstable shiftable mass carried by `said gyro casing for applying a gravity couple to sai gyroscope to cause it to precess. n

7. In a gyro compass; a gyroscope, an element associated with the gyroscope for applying a gravity couple to the gyroscope to cause it to p an inner supporting with an elongated recess,

ring for the roscope and the element, and outerl supporting rings for the inner supporting ring and the gyroscope, said outer rings eing capable of making a complete rotation vertically around the -gyrosco e without affecting the gyroscope and the element.

.8. In a gyro compass a gyroscope consisting of a three phase electrical machine, a casinar "for the gyroscope, a ring surrounding t e casing and supporting the gyroscope upon a horizontal axis, a second ring surrounding the first rin and supporting the same upon a horizonte axis coincident with the first named axis, said second ring being supported upon a vertical axis, and means for conducting the current to Vsaid machine through theI horizontal axes without intertering1 with the freedom of rotation of the secon ring about the gyroscope and the first named ring.

9. In a gyro compass, a' gyroscope consisting of a three hase electrical machine, a ring upon which t e gyroscope is supported, a second vring upon which the firstnamed ring is supported in such a manner that it may be rotated completely around the first named ring and circuit connections for conducting the current to the machine in all positions of the second ring with respect to the d first.

10. In a gyro compass, a gyroscope coinprising, a rotating element `and a casing provided with an aperture' through which a blast of air may be discharged from the casing, a member upon which the casing is su ported upon bearings, and means upon tiri, member and izo-acting with the' air blast from the casing for causing oscillatory movement between the member and the casing to eliminate the the bearings.

11. In a gyro compass, a gyroscope, a ring upon scope is supported upon a. horizontal axis. a4 second ring u on which the firstnamed ring is supporte about a vertical axis consisting of a suspension wire, and means for overcoming the torsion of the wire upon relative movement between the rings consisting of a member attached to each of the rings and a spring connected between the two members. v

12. In a gyral compass, a gyroscopeconsisting of an 4electric motor, a casing for the gyroscope, a ring within which the casiiig is sup orted, a second ring surrounding the first ring and supporting the same upon a horizontal axis, and means for conducting which the gyrod the currentto said mot/or through the axes eli'ect of frictionupon the combination of V 'Illl without interfering with the freedom of y rotation of the second ring about the gyroscope, casing and first ring.

13.`Iii a gyro compass, a gyroscope consisting of an electric motor,

aringuponwhich the gyroscope is supported, a second ring upon which the first ring is sup rted in such a manner that it may be rotate completely around the first ring and gyroscope and circuit connections for conducting current to the motor in all positions of the second ring with respect to the first ring and gyroscope.

14. In a gyro compass, the combination of a gyroscope consistin of a rotating element and a casing, a mem er on which the gyroscope is mounted for oscillation about a horizontal axis, a second member on which the first nam`ed member 1s mounted for turning about a vertical axis and means for causin a jet of air produced by the rotation o the element wlthin the casing to act directly upon the second member to cause it to follow the movements in azimuth of the gyroscope.

15. In a gyro compass, the combination of a gyroscope consisting of a rotating elcment and a casing provided with an aperture through which an air jet may be discharged, a member upon which the gyroscope is supported for oscillation about a horlzontal axis, a second member on which the first named member is mounted for turning about a vertical axis and means for causing the air jet to act directly upon the second member to cause it to follow the movements in azimuth of the gyroscope.

16. In a gyro compass, the combination of a gyroscope comprising a rotating element and a casing having an au' inlet and an air outlet, a member for supporting the gyr o scope for oscillation about a horizontal axis a second member on which the first named t member is mounted for turning about a vertical axis and a device associated with the second member and having a dividing dlaphragm in the path of the air discharged from the casing through the outlet to cause 'the second member to follow the movements in azimuth of the gyroscope.

17. In a gyro compass, the combination of a gyroscope consisting of a rotating element and a casing having an air inlet and an air outlet, a member ou which the gyroscope is mounted, means for mounting the gyroscope and member for oscillation about a horizontal trunnion axis, one of the trunnions of said axisbeing provided with a passage for the discharge of air from the air inlet of the casing, a second member on which the mounting means is mounted for turning about a vertical axis and a device associated with saidlast named member and co-acting with the air discharged from the said trunnion for causing said member to `follow the move'ments in azimuth Aof th gyroscope.

18. In a gyro compass, a gyroscope `con sisting of a rotating element and a casing provi ed with an aperture through which a weasel vertically directed iet of air may be discharged, a member on which the gyroseope is mounted for oscillation about a horizontal axis, a normally balanced shiftable device mounted on the casing and means associated with the device and co-acting with the air jet for applying upon relative movement between the casing and the device a direct torque about a vertical axis to cause precession about the horizontal axis.

19. In a gyro compass, a gyroscope consisting of a rotating element and a casing provided with an aperture through which a vertically directed jet of air may be discharged, a member on which the gyroscope is mounted for oscillation about a horizontal axis, a normally balanced shiftable device mounted on the casing, means associated with the device and co-acting with the air Iiet for applying upon relative movement between the casing and the device a direct torque about a vertical axis to cause precession about the horizontal axis and means for adjusting the torque applying means in relation to the air jet.'

20. In a gyro compass, a gyroscopeconsisting of a rotating element and a casing provided with an aperture through which a vertically directed jet of air may be discharged, a member on which the gyroscopc is mounted for tilting about a horizontal axis, a normally balanced sliiftable mass mounted on the casing, a connection between the mass and the casing for applying a torque about the horizontal` axis to cause precession about a vertical axis when the gyroscope tilts and means.` associated with the mass and co-acting with the air jet for applying a torque about the vertical axis to cause precession of the gyroscope about the horizontal axis.

.21. In a gyro compass, a gyroscope comprising a. rotating element and a casing provided with an aperture through which a vertically directed jet of air may be. discharged, a member on which the gyroscope is mounted for oscillation about a horizontal axis, a liquid level device pivotally mounted on the casing and comprising a pair of receptacles connected by a restricted passage and means associated with the device and co-acting with the air jet for applying upon relative movement between the casing and the device a direct torque about a vertical axis to cause precession of the gyroscope about the horizontal axis upon relative Lmovement between the device and the gyro'scope.

`22. In a gyro compass, a gyroscope consisting of a rotating element and a casing, a. member on which thel gyroscope is mounted for tilting about a horizontal axis, aV

receptacle lconnected to the ends of the members on each side of the casing, one of said members being provided with abore of relativelysmall diameter in communication with the receptacles, means for adjusting the device in normal neutral equilibrium and means effective upon tilt of the roscope for causing the device to appy a torque about the horizontal axis.

23. In a gyro compass, a gyroscope consisting of a rotating element and a casing, a member on which the gyroscope is mounted for tilting about a horizontal axis, a liquid level device comprising a pair of members pivotally mounted at opposite points on the periphery of the casing and a receptacle connected to the ends of the members on each side of the casing, one of said members bein provided with a bore of relatively smal diameter in communication with the receptacles, means for adjusting the device in normal neutral equilibrium and a resilient connection between the casing and the device for applying a torque about an axis of the gyroscope upon relative movement between the device and the gyroscope.

*24. In a gyro compass, a gyroscope con-1 sisting of a rotating element and a casing provided with an aperture through which a vertically directed jet of air may be discharged, a member on which the gyroseope 4 is mounted for tilting about a horizontal axis, a liquid level device comprising a pair of members pivotally mounted at opposite points on the periphery of the casing and a receptacle connected to the ends of the members on each side of the casing, one of said members being rovided with a bore of relatively small diameter in communication with the receptacles, means effective upon tilt of the gyroscope about the horizontal axis for causing the device to appl'y a torque about said axis and means associated with one of the members and co-acting with the air jet for applying a torque about a vertical axis.

25. In a gyro compass, the combination of a gyroscope, a member upon which the gyroscope is supported upon a horizontal axis, a second member upon which the first named member is supported about a vertical' axis including a suspension Wire and means connected between the members *for overcoming the torsion of the wire upon relative movement between the members.

\ 26. In a gyro com ass, a gyroscope, a member upon which t e gyroscope is supported for tilting about a horizontal axis, a. second member, Supporling connections between the members permitting relative rotation of one with respect to the other about a horizontal axis, means for supporting the second member for turning about a vertical axis and means associated with the gyroscope for applying a gravity couple thereto.'

members attached to the casing and -provided with knife edges, a supporting member on which the knife edges rest, a second supporting member on which the flrst'member is mounfed in rotary bearings and a third supporting member on which the second member is mounted for turning about a vertical axis. j

28. In a gyro compass, a roscope, a follow-up element within whixy the gyroscope is mounted, Huid pressure means directly connecting the gyroscope and the follow-up element for causing the element to follow the gyrosco e, fluid pressure means for dam ing the os'ci ations of the roscope and uid pressure means for eliminating theei'ect of friction at the supporting bearings of the i gyroscope. i

29. In a gyro compass, a gyroscope com, prising a rotating element and a casing having outlets for air jets, a follow-up element,

means for mounting the gyrosco e in the' the gyroscopeand means associated with the mountin means and coaeting with another of the air jets for eliminating the e'ect of friction at the supporting bearings of the gyroscope.

31. In a gyro compass, a gyroscope comprising a rotating element and a casing having outlets for air jets, a 4follow-up element, means for mounting the gyroscope in the follow-up element, means associated with the follow-up element and coacting with one of the air jets to cause the element to follow the gyroscope, means carried by the casing andV coacting withv another of the air jets for damping oscillations of the gyroscope and means associated with the mounting means and coacting with another of the air 'ets for eliminating the eect of friction at t e supporting bearings of the gyroscope.

32. In a gyroscopic instrument, a gyroscope consisting of a rotating element and a Y casing provided with knife-edge trunnions, a member on which the easing is supported on the trunnions, a second member on which the first member is supported on the trunnions in line with the axis of the knife-edge uio trunnions and means to cause the first mem for turning about a vertical axis, and means ber to follow movements of the casing about for causing jets ofnir produced by the rotal0 saidraxis.- j tion of the element within the casing to act 33. 111 a gyroscopic instrument, a gyrodirectly -upon the members to cause them. to 5 scope consisting of a. rotatnelement and a follow the movements of the gyroscope about caslng, a. member on which t e gyroscope is their respective axes.

mounted on a horizontal axis, a second member on which the frst member is mounted f 4.MMI-IS BLCKLOCK HENDERSON.

8 y Laax-.tsm

trunnions and means to cause the first memfor turning about a vertical axis, and means ber to follow movements of the casing about for causing jets of air produced by the rota- 10 said axis tion of the element within the casing to act 33. In a gyroscopio instrument, a gyrodirectly Iupon the members to cause them to 5 scope consisting of a rotating element and a follow the movements of the gyroscope about casing, a. member on which the gyroscope is their respective axes. mounted on a horizontal axis, a second mem ber on which the first member is mounted JAMES BLACKLOCK HENDERSON.

Certicate of Correction.' i i i Ps1-,ent No. 1,625,361'. e Granted April 19, 1927, to JAMES BLACKLOCK HENDERSON.

It is hereby certified that error appears in the printed specification of the abovenumbered patent requiring correction as follows: Pa 4, line 120, for the word by ready of; and that the said Letters Patent shou d be read w'ith this correctir therein that the same may conform to the record of the case `in the Patent ce. f i

Signed and sealed this 11th day of October, A. D. 1927.

[SEAL] M. J. MOORE,

l Acting Uomfmlseimwr of Patents.

` 4Certificate of Correction.' l Patent No. 1,625,361. f Granted April 19, 1927, to JAMES BLACKLOCK HENDERSON.

It is hemby certified that error appears in the printed speciication of the abovei numbered patent requiring correction as follows.' Pa e 4, line 120, for the word by read of; and that the said Letrs Patent shou dbe mad w'ith this correction therein that the same may conform to the record of the case in the. Patem Oice. y L

Signed and sealed this 11th day of October, A. D. 1927.

[SEAL] f M. J. MOORE,

` Acting Gommzssomr of Paten/ts. 

